Normally I use git diff to check the changes of uncommited files (not yet git added) with the last commited one.
But after doing git add somefile (but not yet git commited), how to check the diff of that file?
Normally I use git diff to check the changes of uncommited files (not yet git added) with the last commited one.
But after doing git add somefile (but not yet git commited), how to check the diff of that file?
 
    
    You can check
git diff --cached -- yourFile
That will diff between HEAd and the index.

(from 365git.tumblr.com)
The -- helps separating the command from the parameters
See more on the double hyphen syntax in "Deleting a badly named git branch".